These services are made available in real time as a service over the Internet and billed according to use - IT-service on demand (Pay-by-use-model). Thus cloud computing allows organizations to change part of its financial strategy from capital expenses ( CapEx) to operating expenses (OpEx). Cloud computing involves IT services in the broad sense of the term: computing power, storage, bandwidth, or even software (ipanema, Cloud Computing, 2011, p. 74). Over the Internet should be understood in the broadest sense for IP network technology. The notion of provision “on demand” is probably the newest development in cloud computing, because it underpins the other characteristics: access to IT-resources via a network and elasticity.

In principle, one differentiates between the levels of the IT service provided (service models) and the organization of cloud services between the users groups (delivery models).


Cloud computing can be divided into three operations models

• Private Cloud

• Public Cloud

• Hybrid Cloud


• Business Process as a Service

• Software as a Service

• Platform as a Service

• Infrastructure as a Service